Random Access PPDU for WLAN Systems

ABSTRACT

A station is provided. The station includes one or more memories and one or more processors. The one or more processors are configured to one or more of process a first request for buffer status received from an access point and transmit, during the first uplink multi-user transmission to the access point and in response to the first request for buffer status, a first uplink null data packet and that includes a signal that indicates existence of data to be sent from the station to the access point. The first request for buffer status schedules a first uplink multi-user transmission and indicates a plurality of resources that indicates existence of data to be sent to the access point. The one or more processors transmits the first uplink null data packet includes the one or more processors configured to transmit the signal on a first resource of the plurality of resources.

CROSS REFERENCE TO RELATED APPLICATION(S)

This application is a Continuation of pending non-Provisional U.S.application Ser. No. 16/817,525 (Docket No. AGP0077 US) filed Mar. 12,2020, entitled RANDOM ACCESS PPDU FOR WLAN SYSTEMS, which is aContinuation of non-Provisional U.S. application Ser. No. 16/351,280,filed Mar. 12, 2019, now U.S. Pat. No. 10,630,519,which is aContinuation of non-Provisional U.S. application Ser. No. 15/170,890,filed Jun. 1, 2016, now U.S. Pat. No. 10,263,821, which claims thebenefit of U.S. Provisional Application No. 62/170,057, filed Jun. 2,2015, the entirety of each of which is incorporated herein by referencefor all purposes.

FIELD

The present invention relates in general to wireless communicationsystems and methods, and more particularly to, for example, withoutlimitation, random access physical layer convergence procedure (PLCP)protocol data unit (PPDU) for wireless local area network (WLAN) systems

BACKGROUND

Wireless local area network (WLAN) devices are deployed in diverseenvironments. These environments are generally characterized by theexistence of access points and non-access point stations. Increasedinterference from neighboring devices gives rise to performancedegradation. Additionally, WLAN devices are increasingly required tosupport a variety of applications such as video, cloud access, andoffloading. In particular, video traffic is expected to be the dominanttype of traffic in many high efficiency WLAN deployments. With thereal-time requirements of some of these applications, WLAN users demandimproved performance in delivering their applications, includingimproved power consumption for battery-operated devices.

The description provided in the background section should not be assumedto be prior art merely because it is mentioned in or associated with thebackground section. The background section may include information thatdescribes one or more aspects of the subject technology.

SUMMARY

In accordance with embodiments of the present invention, a station isprovided. The station facilitates communication in a wireless networkfor multi-user transmission and includes one or more memories and one ormore processors. The one or more processors are configured to one ormore of process a first request for buffer status received from anaccess point and transmit, during the first uplink multi-usertransmission to the access point and in response to the first requestfor buffer status, a first uplink null data packet and that includes asignal that indicates existence of data to be sent from the station tothe access point. The first request for buffer status schedules a firstuplink multi-user transmission and indicates a plurality of resourcesthat indicates existence of data to be sent to the access point. The oneor more processors transmits the first uplink null data packet includesthe one or more processors configured to transmit the signal on a firstresource of the plurality of resources.

In accordance with another embodiment of the present invention, anaccess point (AP) is provided. The access point (AP) facilitatescommunication in a wireless network for multi-user transmission, andincludes one or more memories and one or more processors, coupled to theone or more memories. The one or more processors are configured to oneor more of send a first request for buffer status to a non-AP stationand receive, during the first uplink multi-user transmission from thenon-AP station and in response to the first request for buffer status, afirst uplink null data packet and that has a signal that indicatesexistence of data to be sent from the station to the AP. The firstrequest for buffer status schedules a first uplink multi-usertransmission and indicates a plurality of resources that indicatesexistence of data to be sent to the AP. The one or more processorsreceive the first uplink null data packet includes the one or moreprocessors configured to receive the signal on a first resource of theplurality of resources.

Additional features and advantages of embodiments of the presentinvention will become more readily apparent from the followingdescription, particularly when taken together with the accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of an example of a wireless communicationnetwork in accordance with embodiments of the present invention.

FIG. 2 is a schematic diagram of an example of a wireless communicationdevice in accordance with embodiments of the present invention.

FIG. 3A is a schematic block diagram of an example of a transmittingsignal processor in a wireless communication device in accordance withembodiments of the present invention.

FIG. 3B is a schematic block diagram of an example of a receiving signalprocessor in a wireless communication device in accordance withembodiments of the present invention.

FIG. 4 is an illustration of an example of a timing diagram ofinterframe space (IFS) relationships in accordance with embodiments ofthe present invention.

FIG. 5 is an illustration of an example of a timing diagram of a carriersense multiple access/collision avoidance (CSMA/CA) based frametransmission procedure for avoiding collision between frames in achannel in accordance with embodiments of the present invention.

FIG. 6 is an illustration of an example of a high efficiency (HE) framein accordance with embodiments of the present invention.

FIG. 7 is an illustration of an example of a random access physicallayer convergence procedure (PLCP) protocol data unit (PPDU) inaccordance with embodiments of the present invention.

FIG. 8 is an illustration of an example of resources that may beutilized for random access in accordance with embodiments of the presentinvention.

FIG. 9 is an illustration of an example of a mapping matrix P_(LTF) inaccordance with embodiments of the present invention.

FIG. 10 is an illustration of an example of comparisons of multipledetection methods in accordance with embodiments of the presentinvention.

FIG. 11 is an illustration of an example of comparisons of multipledetection methods in accordance with embodiments of the presentinvention.

FIG. 12 is an illustration of an example of an allocation of acode-frequency resource in accordance with embodiments of the presentinvention.

FIG. 13 is an illustration of a schematic diagram of an example of anexchange of frames among wireless communication devices forcommunication in a wireless network for multi-user transmission inaccordance with embodiments of the present invention.

FIG. 14 is an illustration of a schematic diagram of an example of anexchange of frames among wireless communication devices forcommunication in a wireless network for multi-user transmission inaccordance with embodiments of the present invention.

FIG. 15 is an illustration of a schematic diagram of an example of anexchange of frames among wireless communication devices forcommunication in a wireless network for multi-user transmission inaccordance with embodiments of the present invention.

FIG. 16A is a flowchart illustrating an example of a method forfacilitating wireless communication for uplink transmission inaccordance with embodiments of the present invention.

FIG. 16B is a flowchart illustrating an example of a method forfacilitating wireless communication for uplink transmission inaccordance with embodiments of the present invention.

In one or more implementations, not all of the depicted components ineach figure may be required, and one or more implementations may includeadditional components not shown in a figure. Variations in thearrangement and type of the components may be made without departingfrom the scope of the subject disclosure. Additional components,different components, or fewer components may be utilized within thescope of the subject disclosure.

DETAILED DESCRIPTION

The detailed description set forth below is intended as a description ofvarious implementations and is not intended to represent the onlyimplementations in which the subject technology may be practiced. Asthose skilled in the art would realize, the described implementationsmay be modified in various different ways, all without departing fromthe scope of the present disclosure. Accordingly, the drawings anddescription are to be regarded as illustrative in nature and notrestrictive.

Systems and methods are disclosed for facilitating uplink (UL)transmissions. One or more implementations of such systems and methodsmay facilitate random access for supporting (e.g., efficientlysupporting) UL multi-user (MU) transmissions. The subject technology maybe utilized in Institute of Electrical and Electronics Engineers (IEEE)systems, such as high efficiency (HE) WLAN.

A station may be allocated a random access channel for a specific timeduration. In some aspects, the random access channel may be allocatedfor stations that have data (e.g., queued data) to send in the uplink.Each station that has some data to send may participate in random accessand select a resource for use in random access transmission. In anaspect, during the random transmission process, collisions may occurbetween the random access transmissions from different stations. In sucha case, resources (e.g., frequency resource, code resource) associatedwith (e.g., selected by, allocated to) the different stations mayoverlap. In another aspect, each station that may potentiallyparticipate in random access transmission may be associated withresources exclusive to (e.g., allocated only to) the station, such thatcollisions can be avoided. In such a case, random access may be referredto as deterministic random access.

In some aspects, random access physical layer convergence procedure(PLCP) protocol data unit (PPDU) design and transmission methods may beprovided to facilitate efficient random access resource utilization. Inan aspect, the random access PPDU may be referred to as a random accesssignal. In some cases, such PPDU design and transmission methods mayhelp reduce or avoid collision between the random access transmissionsfrom different stations.

In one or more implementations, an access point (AP) may transmit atrigger frame to facilitate UL transmission (e.g., UL MU transmission).For instance, the AP may utilize the trigger frame to schedule a UL MUtransmission. The trigger frame may be utilized to solicit responseframes from one or more stations. For simultaneous response frames, theone or more stations may transmit their response frames using UL MUtransmission technology, such as UL MU OFDMA and/or UL MU-MIMO.

A trigger frame may be a frame sent by an AP that seeks data, control,or management frame response(s) from stations that participate in asubsequent UL MU frame. The trigger frame may be utilized to initiatethe simultaneous MU transmission in OFDMA. In an aspect, a trigger framemay include, for example, some or all of the following features: (a) alist of stations (STAB) that an AP seeks a response from; (b) resourceallocation information for each STA (e.g., a subband(s) assigned to eachSTA); and/or (c) attributes of the expected UL MU frame, such as theduration, bandwidth, etc., among other features. A trigger frame may beused to allocate resource for UL MU transmission and to solicit an UL MUtransmission from the participating stations in response to the triggerframe. The trigger frame may include other information needed by theparticipating stations, and the UL MU transmission may occur at apredetermined time interval after the trigger frame. In an aspect, theresource allocation information may include frequency allocationinformation and/or code allocation information. In an aspect, acode-frequency resource may include one or more resource unit(s) (e.g.,a frequency subband(s)) and code to be utilized for transmission. In anaspect, the trigger frame may be referred to as an uplink trigger frame,since the trigger frame may be utilized for facilitating (e.g.,triggering) UL transmission. In an aspect, the trigger frame may beutilized to solicit a null data packet (NDP) from each STA. The term“resource” may refer to, for example, a bandwidth (e.g., a subband(s),frequencies, frequency band(s)), code, time/duration that the STABexpect to occupy a transmission medium, and/or possibly a number ofspatial streams that the STAB may use.

In one aspect, the AP may allocate different portions of a channelbandwidth to different stations. In one aspect, a portion of a channelbandwidth may be a resource unit. In another aspect, a portion of achannel bandwidth may be one or more resource units. In yet anotheraspect, a portion of a channel bandwidth may be one or more blocks of achannel bandwidth. In an aspect, the resource unit may be referred to asa frequency resource unit.

FIG. 1 illustrates a schematic diagram of an example of a wirelesscommunication network 100. In the wireless communication network 100,such as a wireless local area network (WLAN), a basic service set (BSS)includes a plurality of wireless communication devices (e.g., WLANdevices). In one aspect, a BSS refers to a set of STAs that cancommunicate in synchronization, rather than a concept indicating aparticular area. In the example, the wireless communication network 100includes wireless communication devices 111-115, which may be referredto as stations (STAs).

Each of the wireless communication devices 111-115 may include a mediaaccess control (MAC) layer and a physical (PHY) layer according to anIEEE 802.11 standard. In the example, at least one wirelesscommunication device (e.g., device 111) is an access point (AP). An APmay be referred to as an AP STA, an AP device, or a central station. Theother wireless communication devices (e.g., devices 112-115) may benon-AP STAs. Alternatively, all of the wireless communication devices111-115 may be non-AP STAs in an ad-hoc networking environment.

An AP STA and a non-AP STA may be collectively called STAs. However, forsimplicity of description, in some aspects, only a non-AP STA may bereferred to as a STA. An AP may be, for example, a centralizedcontroller, a base station (BS), a node-B, a base transceiver system(BTS), a site controller, a network adapter, a network interface card(NIC), a router, or the like. A non-AP STA (e.g., a client deviceoperable by a user) may be, for example, a device with wirelesscommunication capability, a terminal, a wireless transmit/receive unit(WTRU), a user equipment (UE), a mobile station (MS), a mobile terminal,a mobile subscriber unit, a laptop, a non-mobile computing device (e.g.,a desktop computer with wireless communication capability) or the like.In one or more aspects, a non-AP STA may act as an AP (e.g., a wirelesshotspot).

In one aspect, an AP is a functional entity for providing access to adistribution system, by way of a wireless medium, for an associated STA.For example, an AP may provide access to the internet for one or moreSTAs that are wirelessly and communicatively connected to the AP. InFIG. 1, wireless communications between non-AP STAs are made by way ofan AP. However, when a direct link is established between non-AP STAs,the STAs can communicate directly with each other (without using an AP).

In one or more implementations, OFDMA-based 802.11 technologies areutilized, and for the sake of brevity, a STA refers to a non-AP highefficiency (HE) STA, and an AP refers to an HE AP. In one or moreaspects, a STA may act as an AP.

FIG. 2 illustrates a schematic diagram of an example of a wirelesscommunication device. The wireless communication device 200 includes abaseband processor 210, a radio frequency (RF) transceiver 220, anantenna unit 230, a memory 240, an input interface unit 250, an outputinterface unit 260, and a bus 270, or subsets and variations thereof.The wireless communication device 200 can be, or can be a part of, anyof the wireless communication devices 111-115.

In the example, the baseband processor 210 performs baseband signalprocessing, and includes a medium access control (MAC) processor 211 anda PHY processor 215. The memory 240 may store software (such as MACsoftware) including at least some functions of the MAC layer. The memorymay further store an operating system and applications.

In the illustration, the MAC processor 211 includes a MAC softwareprocessing unit 212 and a MAC hardware processing unit 213. The MACsoftware processing unit 212 executes the MAC software to implement somefunctions of the MAC layer, and the MAC hardware processing unit 213 mayimplement remaining functions of the MAC layer as hardware (MAChardware). However, the MAC processor 211 may vary in functionalitydepending on implementation. The PHY processor 215 includes atransmitting (TX) signal processing unit 280 and a receiving (RX) signalprocessing unit 290. The term TX may refer to transmitting, transmit,transmitted, transmitter or the like. The term RX may refer toreceiving, receive, received, receiver or the like.

The PHY processor 215 interfaces to the MAC processor 211 through, amongothers, transmit vector (TXVECTOR) and receive vector (RXVECTOR)parameters. In one or more aspects, the MAC processor 211 generates andprovides TXVECTOR parameters to the PHY processor 215 to supplyper-packet transmit parameters. In one or more aspects, the PHYprocessor 215 generates and provides RXVECTOR parameters to the MACprocessor 211 to inform the MAC processor 211 of the received packetparameters.

In some aspects, the wireless communication device 200 includes aread-only memory (ROM) (not shown) or registers (not shown) that storeinstructions that are needed by one or more of the MAC processor 211,the PHY processor 215 and/or other components of the wirelesscommunication device 200.

In one or more implementations, the wireless communication device 200includes a permanent storage device (not shown) configured as aread-and-write memory device. The permanent storage device may be anon-volatile memory unit that stores instructions even when the wirelesscommunication device 200 is off. The ROM, registers and the permanentstorage device may be part of the baseband processor 210 or be a part ofthe memory 240. Each of the ROM, the permanent storage device, and thememory 240 may be an example of a memory or a computer-readable medium.A memory may be one or more memories.

The memory 240 may be a read-and-write memory, a read-only memory, avolatile memory, a non-volatile memory, or a combination of some or allof the foregoing. The memory 240 may store instructions that one or moreof the MAC processor 211, the PHY processor 215, and/or anothercomponent may need at runtime.

The RF transceiver 220 includes an RF transmitter 221 and an RF receiver222. The input interface unit 250 receives information from a user, andthe output interface unit 260 outputs information to the user. Theantenna unit 230 includes one or more antennas. When multi-inputmulti-output (MIMO) or multi-user MIMO (MU-MIMO) is used, the antennaunit 230 may include more than one antenna.

The bus 270 collectively represents all system, peripheral, and chipsetbuses that communicatively connect the numerous internal components ofthe wireless communication device 200. In one or more implementations,the bus 270 communicatively connects the baseband processor 210 with thememory 240. From the memory 240, the baseband processor 210 may retrieveinstructions to execute and data to process in order to execute theprocesses of the subject disclosure. The baseband processor 210 can be asingle processor, multiple processors, or a multi-core processor indifferent implementations. The baseband processor 210, the memory 240,the input interface unit 250, and the output interface unit 260 maycommunicate with each other via the bus 270.

The bus 270 also connects to the input interface unit 250 and the outputinterface unit 260. The input interface unit 250 enables a user tocommunicate information and select commands to the wirelesscommunication device 200. Input devices that may be used with the inputinterface unit 250 may include any acoustic, speech, visual, touch,tactile and/or sensory input device, e.g., a keyboard, a pointingdevice, a microphone, or a touchscreen. The output interface unit 260may enable, for example, the display or output of videos, images, audio,and data generated by the wireless communication device 200. Outputdevices that may be used with the output interface unit 260 may includeany visual, auditory, tactile, and/or sensory output device, e.g.,printers and display devices or any other device for outputtinginformation. One or more implementations may include devices thatfunction as both input and output devices, such as a touchscreen.

One or more implementations can be realized in part or in whole using acomputer-readable medium. In one aspect, a computer-readable mediumincludes one or more media. In one or more aspects, a computer-readablemedium is a tangible computer-readable medium, a computer-readablestorage medium, a non-transitory computer-readable medium, amachine-readable medium, a memory, or some combination of the foregoing(e.g., a tangible computer-readable storage medium, or a non-transitorymachine-readable storage medium). In one aspect, a computer is amachine. In one aspect, a computer-implemented method is amachine-implemented method.

A computer-readable medium may include storage integrated into aprocessor and/or storage external to a processor. A computer-readablemedium may be a volatile, non-volatile, solid state, optical, magnetic,and/or other suitable storage device, e.g., RAM, ROM, PROM, EPROM, aflash, registers, a hard disk, a removable memory, or a remote storagedevice.

In one aspect, a computer-readable medium comprises instructions storedtherein. In one aspect, a computer-readable medium is encoded withinstructions. In one aspect, instructions are executable by one or moreprocessors (e.g., 210, 211, 212, 213, 215, 280, 290) to perform one ormore operations or a method. Instructions may include, for example,programs, routines, subroutines, data, data structures, objects,sequences, commands, operations, modules, applications, and/orfunctions. Those skilled in the art would recognize how to implement theinstructions.

A processor (e.g., 210, 211, 212, 213, 215, 280, 290) may be coupled toone or more memories (e.g., one or more external memories such as thememory 240, one or more memories internal to the processor, one or moreregisters internal or external to the processor, or one or more remotememories outside of the device 200), for example, via one or more wiredand/or wireless connections. The coupling may be direct or indirect. Inone aspect, a processor includes one or more processors. A processor,including a processing circuitry capable of executing instructions, mayread, write, or access a computer-readable medium. A processor may be,for example, an application specific integrated circuit (ASIC), adigital signal processor (DSP), or a field programmable gate array(FPGA).

In one aspect, a processor (e.g., 210, 211, 212, 213, 215, 280, 290) isconfigured to cause one or more operations of the subject disclosure tooccur. In one aspect, a processor is configured to cause an apparatus(e.g., a wireless communication device 200) to perform operations or amethod of the subject disclosure. In one or more implementations, aprocessor configuration involves having a processor coupled to one ormore memories. A memory may be internal or external to the processor.Instructions may be in a form of software, hardware or a combinationthereof. Software instructions (including data) may be stored in amemory. Hardware instructions may be part of the hardware circuitrycomponents of a processor. When the instructions are executed orprocessed by one or more processors, (e.g., 210, 211, 212, 213, 215,280, 290), the one or more processors cause one or more operations ofthe subject disclosure to occur or cause an apparatus (e.g., a wirelesscommunication device 200) to perform operations or a method of thesubject disclosure.

FIG. 3A illustrates a schematic block diagram of an example of atransmitting signal processing unit 280 in a wireless communicationdevice. The transmitting signal processing unit 280 of the PHY processor215 includes an encoder 281, an interleaver 282, a mapper 283, aninverse Fourier transformer (1FT) 284, and a guard interval (GI)inserter 285.

The encoder 281 encodes input data. For example, the encoder 281 may bea forward error correction (FEC) encoder. The FEC encoder may include abinary convolutional code (BCC) encoder followed by a puncturing device,or may include a low-density parity-check (LDPC) encoder. Theinterleaver 282 interleaves the bits of each stream output from theencoder 281 to change the order of bits. In one aspect, interleaving maybe applied only when BCC encoding is employed. The mapper 283 maps thesequence of bits output from the interleaver 282 into constellationpoints.

When MIMO or MU-MIMO is employed, the transmitting signal processingunit 280 may use multiple instances of the interleaver 282 and multipleinstances of the mapper 283 corresponding to the number of spatialstreams (Nss). In the example, the transmitting signal processing unit280 may further include a stream parser for dividing outputs of the BCCencoders or the LDPC encoder into blocks that are sent to differentinterleavers 282 or mappers 283. The transmitting signal processing unit280 may further include a space-time block code (STBC) encoder forspreading the constellation points from the number of spatial streamsinto a number of space-time streams (NsTs) and a spatial mapper formapping the space-time streams to transmit chains. The spatial mappermay use direct mapping, spatial expansion, or beamforming depending onimplementation. When MU-MIMO is employed, one or more of the blocksbefore reaching the spatial mapper may be provided for each user.

The 1FT 284 converts a block of the constellation points output from themapper 283 or the spatial mapper into a time domain block (e.g., asymbol) by using an inverse discrete Fourier transform (IDFT) or aninverse fast Fourier transform (IFFT). If the STBC encoder and thespatial mapper are employed, the 1FT 284 may be provided for eachtransmit chain.

When MIMO or MU-MIMO is employed, the transmitting signal processingunit 280 may insert cyclic shift diversities (CSDs) to preventunintentional beamforming. The CSD insertion may occur before or afterthe inverse Fourier transform operation. The CSD may be specified pertransmit chain or may be specified per space-time stream. Alternatively,the CSD may be applied as a part of the spatial mapper.

The GI inserter 285 prepends a GI to the symbol. The transmitting signalprocessing unit 280 may optionally perform windowing to smooth edges ofeach symbol after inserting the GI. The RF transmitter 221 converts thesymbols into an RF signal and transmits the RF signal via the antennaunit 230. When MIMO or MU-MIMO is employed, the GI inserter 285 and theRF transmitter 221 may be provided for each transmit chain.

FIG. 3B illustrates a schematic block diagram of an example of areceiving signal processing unit 290 in a wireless communication device.The receiving signal processing unit 290 of the PHY processor 215includes a GI remover 291, a Fourier transformer (FT) 292, a demapper293, a deinterleaver 294, and a decoder 295.

The RF receiver 222 receives an RF signal via the antenna unit 230 andconverts the RF signal into one or more symbols. In some aspects, the GIremover 291 removes the GI from the symbol. When MIMO or MU-MIMO isemployed, the RF receiver 222 and the GI remover 291 may be provided foreach receive chain.

The FT 292 converts the symbol (e.g., the time domain block) into ablock of the constellation points by using a discrete Fourier transform(DFT) or a fast Fourier transform (FFT) depending on implementation. Inone or more implementations, the FT 292 is provided for each receivechain.

When MIMO or MU-MIMO is employed, the receiving signal processing unit290 may further include a spatial demapper for converting the Fouriertransformed receiver chains to constellation points of the space-timestreams, and a STBC decoder (not shown) for despreading theconstellation points from the space-time streams into the spatialstreams.

The demapper 293 demaps the constellation points output from the FT 292or the STBC decoder to the bit streams. If the LDPC encoding is used,the demapper 293 may further perform LDPC tone demapping before theconstellation demapping. The deinterleaver 294 deinterleaves the bits ofeach stream output from the demapper 293. In one or moreimplementations, deinterleaving may be applied only when BCC decoding isused.

When MIMO or MU-MIMO is employed, the receiving signal processing unit290 may use multiple instances on the demapper 293 and multipleinstances of the deinterleaver 294 corresponding to the number ofspatial streams. In the example, the receiving signal processing unit290 may further include a stream deparser for combining the streamsoutput from the deinterleavers 294.

The decoder 295 decodes the streams output from the deinterleaver 294and/or the stream deparser. For example, the decoder 295 may be an FECdecoder. The FEC decoder may include a BCC decoder or an LDPC decoder.

FIG. 4 illustrates an example of a timing diagram of interframe space(IFS) relationships. In this example, a data frame, a control frame, ora management frame can be exchanged between the wireless communicationdevices 111-115 and/or other WLAN devices.

Referring to the timing diagram 400, during the time interval 402,access is deferred while the medium (e.g., a wireless communicationchannel) is busy until a type of IFS duration has elapsed. At timeinterval 404, immediate access is granted when the medium is idle for aduration that is equal to or greater than a distributed coordinationfunction IFS (DIFS) 410 duration or arbitration IFS (AIFS) 414 duration.In turn, a next frame 406 may be transmitted after a type of IFSduration and a contention window 418 have passed. During the time 408,if a DIFS has elapsed since the medium has been idle, a designated slottime 420 is selected and one or more backoff slots 422 are decrementedas long as the medium is idle.

The data frame is used for transmission of data forwarded to a higherlayer. In one or more implementations, a WLAN device transmits the dataframe after performing backoff if DIFS 410 has elapsed from a time whenthe medium has been idle.

The management frame is used for exchanging management information thatis not forwarded to the higher layer. Subtype frames of the managementframe include a beacon frame, an association request/response frame, aprobe request/response frame, and an authentication request/responseframe.

The control frame is used for controlling access to the medium. Subtypeframes of the control frame include a request to send (RTS) frame, aclear to send (CTS) frame, and an ACK frame. In the case that thecontrol frame is not a response frame of the other frame (e.g., aprevious frame), the WLAN device transmits the control frame afterperforming backoff if the DIFS 410 has elapsed. In the case that thecontrol frame is the response frame of the other frame, the WLAN devicetransmits the control frame without performing backoff if a short IFS(SIFS) 412 has elapsed. For example, the SIFS may be 16 microseconds.The type and subtype of frame may be identified by a type field and asubtype field in a frame control field of the frame.

On the other hand, a Quality of Service (QoS) STA may transmit the frameafter performing backoff if AIFS 414 for access category (AC), e.g.,AIFS[AC], has elapsed. In this case, the data frame, the managementframe, or the control frame that is not the response frame may use theAIFS[AC].

In one or more implementations, a point coordination function (PCF)enabled AP STA transmits the frame after performing backoff if a PCF IFS(PIFS) 416 has elapsed. In this example, the PIFS 416 duration is lessthan the DIFS 410 but greater than the SIFS 412. In some aspects, thePIFS 416 is determined by incrementing the SIFS 412 duration by adesignated slot time 420.

FIG. 5 illustrates an example of a timing diagram of a carrier sensemultiple access/collision avoidance (CSMA/CA) based frame transmissionprocedure for avoiding collision between frames in a channel. In FIG. 5,anyone of the wireless communication devices 111-115 in FIG. 1 can bedesignated as one of STA1, STA2 or STA3. In this example, the wirelesscommunication device 111 is designated as STA1, the wirelesscommunication device 112 is designated as STA2, and the wirelesscommunication device 113 is designated as STA3. While the timing of thewireless communication devices 114 and 115 is not shown in FIG. 5, thetiming of the devices 114 and 115 may be the same as that of STA2.

In this example, STA1 is a transmit WLAN device for transmitting data,STA2 is a receive WLAN device for receiving the data, and STA3 is a WLANdevice that may be located at an area where a frame transmitted from theSTA1 and/or a frame transmitted from the STA2 can be received by theSTA3.

The STA1 may determine whether the channel (or medium) is busy bycarrier sensmg. The STA1 may determine the channel occupation based onan energy level on the channel or correlation of signals in the channel.In one or more implementations, the STA1 determines the channeloccupation by using a network allocation vector (NAV) timer.

When determining that the channel is not used by other devices duringthe DIFS 410 (e.g., the channel is idle), the STA1 may transmit an RTSframe 502 to the STA2 after performing backoff. Upon receiving the RTSframe 502, the STA2 may transmit a CTS frame 506 as a response of theCTS frame 506 after the SIFS 412.

When the STA3 receives the RTS frame 502, the STA3 may set a NAV timerfor a transmission duration representing the propagation delay ofsubsequently transmitted frames by using duration information involvedwith the transmission of the RTS frame 502 (e.g., NAV(RTS) 510). Forexample, the STA3 may set the transmission duration expressed as thesummation of a first instance of the SIFS 412, the CTS frame 506duration, a second instance of the SIFS 412, a data frame 504 duration,a third instance of the SIFS 412 and an ACK frame 508 duration.

Upon receiving a new frame (not shown) before the NAV timer expires, theSTA3 may update the NAV timer by using duration information included inthe new frame. The STA3 does not attempt to access the channel until theNAV timer expires.

When the STA1 receives the CTS frame 506 from the STA2, the STA1 maytransmit the data frame 504 to the STA2 after the SIFS 412 elapses froma time when the CTS frame 506 has been completely received. Uponsuccessfully receiving the data frame 504, the STA2 may transmit the ACKframe 508 after the SIFS 412 elapses as an acknowledgment of receivingthe data frame 504.

When the NAV timer expires, the STA3 may determine whether the channelis busy by the carrier sensing. Upon determining that the channel is notused by the other WLAN devices (e.g., STA1, STA2) during the DIFS 410after the NAV timer has expired, the STA3 may attempt the channel accessafter a contention window 418 has elapsed. In this example, thecontention window 418 may be based on a random backoff.

FIG. 6 illustrates an example of a high efficiency (HE) frame 600. TheHE frame 600 is a physical layer convergence procedure (PLCP) protocoldata unit (or PPDU) format. An HE frame may be referred to as an OFDMAframe, a PPDU, a PPDU format, an OFDMA PPDU, an MU PPDU, another similarterm, or vice versa. An HE frame may be simply referred to as a framefor convenience. A transmitting station (e.g., AP, non-AP station) maygenerate the HE frame 600 and transmit the HE frame 600 to a receivingstation. The receiving station may receive, detect, and process the HEframe 600. The HE frame 600 may include an L-STF field, an L-LTF field,an L-SIG field, an RL-SIG field, an HE-SIG-A field, an HE-SIG-B field,an HE-STF field, an HE-LTF field, and an HE-DATA field. The HE-SIG-Afield may include N_(HESIGA) symbols, the HE-SIG-B field may includeN_(HESIGB) symbols, the HE-LTF field may include N_(HELTF) symbols, andthe HE-DATA field may include N_(DATA) symbols. In an aspect, theHE-DATA field may also be referred to as a payload field, data field,data, data signal, data portion, payload, PSDU, or Media Access Control(MAC) Protocol Data Units (MPDU) (e.g., MAC frame).

In one or more implementations, an AP may transmit a frame for downlink(DL) using a frame format shown in this figure or a variation thereof(e.g., without any or some portions of an HE header). A STA may transmita frame for uplink (UL) using a frame format shown in this figure or avariation thereof (e.g., without any or some portions of an HE header).

The table below provides examples of characteristics associated with thevarious components of the HE frame 600:

DFT Subcarrier Element Definition Duration Period GI Spacing DescriptionLegacy Non-high 8 us — — Equivalent L-STF of a non- (L)-STF throughputto 1.250 trigger-based (HT) Short KHz PPDU has a Training periodicity of0.8 Field us with 10 periods L-LTF Non-HT 8 us 3.2 us 1.6 us 312.5 KHzLong Training Field L-SIG Non-HT 4 us 3.2 us 0.8 us 312.5 KHz SIGNALField RL-SIG Repeated 4 us 3.2 us 0.8 us 312.5 KHz Non-HT SIGNAL FieldHE-SIG-A HE N_(RESIGA) * 3.2 us 0.8 us 312.5 KHz HE-SIG-A is SIGNAL 4 usduplicated on A Field each 20 MHz segment after the legacy preamble toindicate HE common control information. N_(HESIGA) means the number ofOFDM symbols of the HE-SIG-A field and is equal to 2 or 4. HE-SIG-B HEN_(HESIGB) * 3.2 us 0.8 us 312.5 KHz N_(HESIGB) SIGNAL 4 us means the BField number of OFDM symbols of the HE-SIG-B field and is variable. DLMU packet contains HE-SIG-B. Single user (SU) packets and UL Triggerbased packets do not contain HE-SIG-B. HE-STF HE Short 4 or 8 us — —Non- HE-STF of a non- Training trigger- trigger-based Field based PPDUhas a PPDU periodicity of 0.8 (equivalent us with 5 periods. to) 1,250 Anon-trigger- KHz based PPDU is not Trigger- sent in response to based atrigger frame. PPDU: The HE-STF of a (equivalent trigger-based to) 625KHz PPDU has a periodicity of 1.6 us with 5 periods. A trigger-basedPPDU is a UL PPDU sent in response to a trigger frame. HE-LTF HE LongN_(HELTF) * 2xLTF: Supports 2xLTF HE PPDU Training (DFT 6.4 us, 0.8,1.6, (equivalent may support Field period + 4xLTF: 3.2 us to) 156.252xLTF mode GI) us 12.8 us KHz, and 4xLTF 4xLTF: mode. 78.125 KHz In the2xLTF mode, HE-LTF symbol excluding GI is equivalent to modulating everyother tone in an OFDM symbol of 12.8 us excluding GI, and then removingthe second half of the OFDM symbol in time domain. N_(HELTF) means thenumber of HE-LTF symbols and is equal to 1, 2, 4, 6, 8. HE- HE DATAN_(DATA) * 12.8 us Supports 78.125 KHz N_(DATA) means the DATA Field(DFT 0.8, 1.6, number of HE data period + 3.2 us symbols GI) us

Referring to FIG. 6, the HE frame 600 contains a header and a datafield. The header includes a legacy header comprised of the legacy shorttraining field (L-STF), the legacy long training field (L-LTF), and thelegacy signal (L-SIG) field. These legacy fields contain symbols basedon an early design of an IEEE 802.11 specification. Presence of thesesymbols may facilitate compatibility of new designs with the legacydesigns and products. The legacy header may be referred to as a legacypreamble. In one or more aspects, the term header may be referred to asa preamble.

In one or more implementations, the legacy STF, LTF, and SIG symbols aremodulated/carried with FFT size of 64 on a 20 MHz sub-channel and areduplicated every 20 MHz if the frame has a channel bandwidth wider than20 MHz (e.g., 40 MHz, 80 MHz, 160 MHz). Therefore, the legacy field(i.e., the STF, LTF, and SIG fields) occupies the entire channelbandwidth of the frame. The L-STF field may be utilized for packetdetection, automatic gain control (AGC), and coarse frequency-offset(FO) correction. In one aspect, the L-STF field does not utilizefrequency domain processing (e.g., FFT processing) but rather utilizestime domain processing. The L-LTF field may be utilized for channelestimation, fine frequency-offset correction, and symbol timing. In oneor more aspects, the L-SIG field may contain information indicative of adata rate and a length (e.g., in bytes) associated with the HE frame600, which may be utilized by a receiver of the HE frame 600 tocalculate a time duration of a transmission of the HE frame 600.

The header may also include an HE header comprised of an HE-SIG-A fieldand a HE-SIG-B field. The HE header may be referred to as a non-legacyheader. These fields contain symbols that carry control informationassociated with each PLCP service data unit (PSDU) and/or radiofrequency (RF), PHY, and MAC properties of a PPDU. In one aspect, theHE-SIG-A field can be carried/modulated using an FFT size of 64 on a 20MHz basis. The HE-SIG-B field can be carried/modulated using an FFT sizeof e.g., 64 or 256 on a 20 MHz basis depending on implementation. TheHE-SIG-A and HE-SIG-B fields may occupy the entire channel bandwidth ofthe frame. In some aspects, the size of the HE-SIG-A field and/or theHE-SIG-B field is variable (e.g., can vary from frame to frame). In anaspect, the HE-SIG-B field is not always present in all frames. Tofacilitate decoding of the HE frame 600 by a receiver, the size of(e.g., number of symbols contained in) the HE-SIG-B field may beindicated in the HE-SIG-A field. In some aspects, the HE header alsoincludes the repeated L-SIG (RL-SIG) field, whose content is the same asthe L-SIG field.

The HE header may further include HE-STF and HE-LTF fields, whichcontain symbols used to perform necessary RF and PHY processing for eachPSDU and/or for the whole PPDU The HE-LTF symbols may bemodulated/carried with an FFT size of 256 for 20 MHz bandwidth andmodulated over the entire bandwidth of the frame. Thus, the HE-LTF fieldmay occupy the entire channel bandwidth of the frame. In one aspect, theHE-LTF field may occupy less than the entire channel bandwidth. In oneaspect, the HE-LTF field may be transmitted using a code-frequencyresource. In one aspect, a HE-LTF sequence may be utilized by a receiverto estimate MIMO channel between the transmitter and the receiver.Channel estimation may be utilized to decode data transmitted andcompensate for channel properties (e.g., effects, distortions). Forexample, when a preamble is transmitted through a wireless channel,various distortions may occur, and a training sequence in the HE-LTFfield is useful to reverse the distortion. This may be referred to asequalization. To accomplish this, the amount of channel distortion ismeasured. This may be referred to as channel estimation. In one aspect,channel estimation is performed using an HE-LTF sequence, and thechannel estimation may be applied to other fields that follow the HE-LTFsequence.

The HE-STF symbols may have a fixed pattern and a fixed duration. Forexample, the HE-STF symbols may have a predetermined repeating pattern.In one aspect, the HE-STF symbols do not require FFT processing. The HEframe 600 may include the data field, represented as HE-DATA, thatcontains data symbols. The data field may also be referred to as apayload field, data, payload or PSDU.

In one or more aspects, additional one or more HE-LTF fields may beincluded in the header. For example, an additional HE-LTF field may belocated after a first HE-LTF field. In one or more implementations, a TXsignal processing unit 280 (or an 1FT 284) illustrated in FIG. 3A maycarry out the modulation described in this paragraph as well as themodulations described in other paragraphs above. In one or moreimplementations, an RX signal processing unit 290 (or an FT 292) mayperform demodulation for a receiver.

In one or more implementations, random access PPDU format design andtransmission methods are provided to facilitate efficient random accessresource utilization. In some aspects, random access resources allocatedper station by an AP may be expected to be small in capacity (e.g., asmall frequency subband(s)). In an aspect, utilization of smaller randomaccess resources may allow a lower collision probability between randomaccess transmission of different stations than a case in which largerrandom access resources are utilized. For instance, for a given channelbandwidth, the channel bandwidth can be divided into a large number ofsmall random access resources rather than a small number of large randomaccess resources. The large number of small random access resources maybe allocated to the stations for random access transmission. In anaspect, the random access PPDU may be referred to as a random accesssignal.

In one or more aspects, alternatively or in addition, a random accessPPDU format may be utilized to reduce (e.g., further reduce) thecollision probability and improve random access signaldetection/decoding performance. In some aspects, the random access PPDUmay include a first part and a second part. The first part may beidentical between stations. The second part may be different between thestations. Each station may transmit the second part on a random accessresource (e.g., allocated by the AP and/or selected by the station). Inone aspect, the first part may be referred to as a common preambleportion and the second part may be referred to as a STA specific portionor user specific portion.

In some aspects, the STA specific portion may contain more than oneHE-LTF symbol even though or even in a case when the random accesssignal is limited to one spatial stream per station. In one aspect, thecommon preamble portion may be aligned and identical between randomaccess transmissions (e.g., from different stations). In this aspect,the total number of HE-LTF symbols may also be the same (e.g., alignedand identical between the random access transmissions). However, in anaspect, a transmitted signal for HE-LTF may be different from that ofother stations such that the HE-LTF between stations can be orthogonalto each other. The AP may indicate (e.g., in a trigger frame) the numberof HE-LTF symbols to be transmitted by the stations.

FIG. 7 illustrates an example of a random access PPDU 700. Thedescription from FIG. 6 generally applies to FIG. 7, with examples ofdifferences between FIG. 6 and FIG. 7 and other description providedherein for purposes of clarity and simplicity. The vertical dimensionrepresents the frequency dimension. In one aspect, a non-AP stationutilizes the random access PPDU 700.

The random access PPDU 700 includes a common preamble portion and a STAspecific portion. The common preamble portion may include a legacypreamble portion (e.g., L-STF, L-LTF, L-SIG) and an HE-specific preambleportion (e.g., RL-SIG, HE-SIG-A, HE-SIG-B). In some aspects, the variousfields of the common preamble portion (e.g., legacy preamble portion,HE-specific preamble portion) may occupy an entire channel bandwidth ofthe random access PPDU 700. In some aspects, the various fields of theSTA specific portion (e.g., HE-STF, HE-LTF, HE-DATA) may occupy lessthan the entire channel bandwidth. For instance, the STA specificportion may occupy one or more resource units within thechannelbandwidth (e.g., a frequency subband(s)) associated with (e.g.,allocated to, selected by) the station that transmits the random accessPPDU 700. In one aspect, the random access PPDU 700 does not includeHE-DATA (e.g., does not include any data symbols). In such an aspect,the random access PPDU 700 may be, or may be referred to as, a null datapacket (NDP) or a non-data packet. In one aspect, the random access PPDU700 may include an L-STF, L-LTF, L-SIG, RL-SIG, and HE-SIG-A field.

In some aspects, the HE-LTF may span more spatial streams than thenumber of receive (Rx) antennas at the AP. As an example, N HE-LTFsymbols may be utilized even if the random access PPDU 700 istransmitted using one spatial stream, where N>1. In other words, N maybe larger than the total number of receive antennas at the AP. Asanother example, the AP may only have two receive antennas, but requestthat stations use eight HE-LTF symbols (e.g., as if there are a total ofeight transmit (Tx) antennas). In some cases, the station may select(e.g., randomly select, pseudorandomly select) a spatial stream toutilize for transmission. In contrast, typically, an AP with M (e.g.,four) receive antennas may only be able to process up to M spatialstreams and, therefore, would expect to receive an HE-LTF that spans Mspatial streams.

In one or more aspects, the stations may transmit the HE-LTF symbolsusing respective random access resource(s) associated with the stations.In an aspect, the random access resource may have two dimensions: onedimension in frequency domain and one dimension in code domain. In thisaspect, the random access resource may include, or may be referred toas, a code-frequency resource(s).

FIG. 8 illustrates an example of resources that may be utilized forrandom access. The random access resources may be utilized fortransmission of HE-LTF symbols in a random access channel (e.g., ofchannel bandwidth 20 MHz). The vertical dimension represents the codedimension and the horizontal dimension represents the frequencydimension.

In FIG. 8, in the frequency domain, the channel bandwidth is dividedinto nine resource units (e.g., frequency subbands). In an aspect, ifeight HE-LTF orthogonal frequency division multiplexing (OFDM) symbolsare transmitted, HE-LTF may have in total 72 random access resourcecandidates (e.g., 8 code spaces×9 resource units=72 resourcecandidates). Each random access resource candidate is represented as arectangular block in FIG. 8. In an aspect, rectangular block in FIG. 8is associated with a resource unit (RU) index and a spatial stream (SS)index. For instance, a block 802 is associated with a resource unit ofresource unit index 9 (RU9) and spatial stream of spatial stream index 2(SS2). Each station may select (e.g., randomly select, pseudorandomlyselect) one of the eight code spaces. In an aspect, a code space may bereferred to simply as a code. In an aspect, the eight code spaces areorthogonal to each other. Such code spaces may traditionally be mappedto different spatial streams in downlink/uplink MIMO transmissions.

In an aspect, correct decoding of a single stream transmission (e.g.,rank 1 transmission) may be achieved using only one HE-LTF symbol insome cases. In an aspect, additional HE-LTF symbols may be utilized tofacilitate detecting a presence of a data portion (e.g., HE-DATA field)in the same frequency resource unit and/or to improve decoding of thedata portion when random access signals have collided in frequency.

FIG. 9 illustrates an example of a mapping matrix P_(LTF). In FIG. 9,the P_(LTF) matrix is an 8×8 matrix. In an aspect, the P_(LTF) matrixmay be referred to as a P_(SXS) matrix. The column dimension of theP_(LTF) matrix may correspond to the number of HE-LTF symbols and/ortime domain. The row dimension of the P_(LTF) matrix may correspond tothe number of spatial streams. In this regard, each row of the P_(LTF)matrix may be associated with a respective code space. In an aspect, ifeight HE-LTF OFDM symbols are used, the P_(LTF) matrix of FIG. 9 may beutilized to modulate the HE-LTF OFDM symbols. For instance, if a stationselects (e.g., randomly selects, pseudorandomly selects) the third codespace, then the station may use the eight elements of the third row ofthe P_(LTF) matrix to modulate the eight HE-LTF symbols.

In some aspects, to help ensure that the HE-LTF from different stationsare orthogonal, the AP may indicate to the stations the number of HE-LTFsymbols (or a dimension of a virtual antenna) in a trigger frame. In anaspect, the number of HE-LTF symbols can be larger than the number ofreceive antennas of the AP. The station may select (e.g., randomlyselect, pseudorandomly select) a code (e.g., a row of the P_(LTF)matrix) to apply to the transmission of the HE-LTF symbols. In anaspect, the station may select (e.g., randomly select, pseudorandomlyselect) a spatial stream among all possible spatial streams.

In some aspects, a PPDU capture effect may occur when the AP is able toreceive and successfully decode a frame, even though the frame hascollided with another frame. For uplink random access, this is typicallynot possible since different stations transmit simultaneously and theHE-LTF of the different stations may be air-combined (e.g., radiofrequency (RF)-combined). The air-combined HE-LTFs of the differentstations may cause incorrect (e.g., completely wrong in some cases)channel estimation results.

If two stations occupying the same resource unit (e.g., a frequencyposition(s), a frequency subband(s)) use different code to send theHE-LTF, the AP may be able to perform channel estimation correctly. Inan aspect, whether respective data (e.g., payload, HE-DATA) of the twostations may be decoded correctly by the AP may be based on a modulationand coding scheme (MCS) that is utilized. For instance, in some cases,the HE-LTF sent using different code may be orthogonal (e.g., may beguaranteed to be orthogonal). In such cases, if the data is sent in asufficiently low MCS, the AP may be able to decode the respective dataof each station.

Although the foregoing description makes reference to collisionsinvolving transmissions from two stations, the collisions may alsoinvolve transmissions from more than two stations. In such a case, ifthese stations (e.g., more than two stations) occupy the same resourceunit but use different code to send the HE-LTF, the AP may be able toperform channel estimation correctly.

FIG. 10 illustrates an example of a comparison of two detection methods.In FIG. 10, the detection methods include a detection method thatutilizes code separation and a detection method that does not utilizecode separation, respectively referred to as code separated detectionmethod and non-code separated detection method. In the non-codeseparated detection method, STA1 and STA2 may each transmit (e.g.,simultaneously transmit) a respective uplink frame that includes arespective HE-LTF 1002 and 1006 and respective data 1004 and 1008. STA1and STA2 may transmit the uplink frames in the same resource units(e.g., frequency subbands). The HE-LTFs 1002 and 1006 may be modulatedusing the same code and may be air-combined (e.g., RF-combined). Sincethe same code and same resource units are used in the transmission ofthe HE-LTFs 1002 and 1006, channel estimation based on the HE-LTFs 1002and 1006 may be incorrect (e.g., corrupted). In such a case where thechannel estimation is incorrect, the AP is generally unable to decodethe data 1004 and 1008 correctly. For instance, in this case, the data1004 and 1008 may be almost impossible to decode correctly.

In the code separated detection method, STA1 and STA2 may each transmit(e.g., simultaneously transmit) a respective uplink frame that includesa respective HE-LTF and the respective data 1004 and 1008. STA1 and STA2may transmit the uplink frames in the same resource units. In thisregard, STA1 and STA2 may have selected (e.g., randomly selected) thesame resource units. STA1 and STA2 may modulate their respective HE-LTFusing different code. For instance, in FIG. 10, STA1 utilizes a secondcode space (e.g., associated with a second row of the P_(LTF) matrix)and STA2 utilizes a seventh code space (e.g., associated with a seventhrow of the P_(LTF) matrix). In an aspect, the eight code spaces areorthogonal to each other. In this aspect, the second code space (e.g.,used by STA1) and the seventh code space (e.g., used by STA2) areorthogonal to each other. In an aspect, STA1 and STA2 may select (e.g.,randomly select, pseudorandomly select) the code space to utilize. Whenthe HE-LTFs utilized by STA1 and STA2 are orthogonal, the AP may obtaincorrect channel estimation for STA1 and STA2. In such a case, althoughthe data 1004 and 1008 occupy the same resource unit and thus interferewith each other, the AP may be able to correctly decode the data 1004and 1008 since the AP has the correct channel estimation for both thedata 1004 and 1008. For instance, the AP may be able to correctly decodethe data 1004 and 1008 in cases where the MCS is lower.

In one or more aspects, the AP may utilize the HE-LTF OFDM symbols todetect presence of data transmissions. FIG. 11 illustrates anotherexample of a comparison between two detection methods. In FIG. 11, thedetection methods include a code separated detection method and anon-code separated detection method. In some aspects, the detection ofthe presence of a random access signal can be performed by detection ofthe HE-LTF signals in a particular code space and/or frequency domain(e.g., resource unit). Detection performance may be enhanced whenmultiple HE-LTF OFDM symbols are utilized, such as in the code separateddetection method.

In an aspect, similar to detection of L-STF and L-LTF, a structure(e.g., repetitive structure) of the HE-LTFs may allow improvement indetection of a signal (e.g., detection of presence of data). When thepresence of data is detected by the AP, the AP may decode those resourceunit(s) where HE-LTF has been detected (e.g., rather than decoding allresource units in which data may possibly be transmitted). In somecases, the use of a single HE-LTF symbol is not sufficiently reliablefor detecting the presence of data in a certain resource (e.g.,frequency resource unit). For instance, in the non-code separateddetection method, the AP may have to decode all possible resource units(e.g., potential candidates) to determine the resource unites) withinwhich data has been transmitted.

In one or more implementations, random access may be utilized bystations to indicate existence of information to send in the uplink. Insome aspects, the AP may transmit a trigger frame to request/solicit thestations to transmit such an indication. In some aspects, such as inresponse to the trigger frame, the stations may transmit a short randomaccess PPDU to indicate existence of information to send in the uplink.In such aspects, the trigger frame may be referred to as a random accesstrigger frame or a random access trigger. In one aspect, the shortrandom access PPDU may include a small payload (e.g., small HE-DATA). Byway of non-limiting example, the payload may include an indication ofwhether the station has data to send in the uplink and/or a bufferstatus report of the station. In another aspect, the random access PPDUmay be a non-data containing PPDU (e.g., NDP packet). For instance,instead of a station transmitting a short data packet (e.g., data packetwith a small HE-DATA field), the station may transmit the commonpreamble portion and only up to and including the HE-LTF of the STAspecific portion of the preamble. In other words, the station does notsend any data (e.g., data field, HE-DATA). Use of the non-datacontaining PPDU may allow a reduction in overhead associated withsignaling, to the AP, the existence of information to send in theuplink. In an aspect, the trigger frame may include an indication to thestations whether to send a short random access PPDU that includes asmall payload or a short random access PPDU with no payload (e.g.,non-data containing PPDU, NDP frame) in response to the trigger frame.

In an aspect, the station may transmit the short random access PPDU(e.g., nondata containing PPDU) to the AP when (e.g., only when) thestation has data to send in the uplink. In an aspect, the AP maytransmit a trigger frame to facilitate UL MU transmission based on theshort random access PPDU(s) received (or not received) from thestations.

In one or more aspects, the AP may assign a specific code-frequencyresource to a specific station or group of stations. The specificcode-frequency resource may be associated with one or more spatialstream indices and one or more resource unit indices. In these aspects,the spatial stream index or indices and resource unit index or indicesmay be used to identify the specific station or group of stations duringrandom access. In this regard, the specific station or group of stationsmay utilize the specific code-frequency resource(s) that areassigned/allocated to indicate existence of data to be sent to the AP.The code-frequency resource may be utilized for transmission of HE-LTFsymbols. In an aspect, the specific code-frequency resource may bereferred to as a specific code-frequency LTF resource or specificcode-frequency HE-LTF resource. For example, each code-frequencyresource can be assigned to a specific association identification (AID)of a station.

In one embodiment, the station may transmit a short random access PPDUto the AP using a code to indicate that the station has data to send inthe uplink, and another code to indicate that the station does not havedata to send in the uplink. In an aspect, this may require that the APassign a set of codes, for example one code for positive acknowledgementof data to send and one code for negative acknowledgement of data tosend, to each station or group of stations during a short random access.

FIG. 12 illustrates an example of an allocation of a code-frequencyresource. In FIG. 12, 72 code-frequency resources are shown. Eachcode-frequency resource is associated with a resource unit index and aspatial stream index. In an aspect, the term index may be referred to asa number, such that each code-frequency resource is associated with aresource unit number and a spatial stream number. The AP may assigndifferent stations (or different AIDs) to different frequency and/orcode blocks. Each station (or each AID) may be mapped to a particularresource unit index and a spatial stream index. The mapping may change(including no mapping) depending on signaling (e.g., in a triggerframe). In some cases, each AID may be uniquely mapped to a RU index andSS index. In FIG. 12, a station or group of stations associated withAID1 may be assigned the code-frequency resource (RU9, SS2). In somecases, the mapping may not be unique, such that a code-frequencyresource (RU #, SS #) may be shared by multiple AIDs. In such a case,the shared codefrequency resource(s) may be assigned in a manner suchthat collision probability is low.

In some aspects, the detection of an HE-LTF in a specific code-frequencyresource may indicate that a station has data to send to the AP.Different mapping of station (or group of stations) to a code-frequencyresource can be possible. In an aspect, the different mapping, denotedas different random access types, may be indicated in a trigger frametransmitted by the AP. In an aspect, the random access type may bereferred to as a random access group or random access sequence number.The random access type may be utilized to aid stations in identifyingand differentiating between different random access opportunities. Eachstation may be associated with a random access type, a code, and aresource unit. A station, upon reception of the trigger frame, mayidentify the mapping between code-frequency resource and associated AID(or group of AIDs) and transmit random access signal according to theidentified mapping.

FIG. 13 illustrates a schematic diagram of an example of an exchange offrames among wireless communication devices for communication in awireless network for UL MU transmission. The AP may transmit a triggerframe 1302. The trigger frame 1302 may include an indication of a randomaccess type. In FIG. 13, the trigger frame 1302 includes an indicationof a random access type 1, which includes a mapping of resourcesallocated to the group of stations formed of STA1, STA2, STA3, . . . ,STA200. The trigger frame 1302 may include code-frequency resourceallocation for each of the stations in the group of stations associatedwith the random access type 1. For instance, STA1, STA2, STA3, andSTA200 may be allocated (RU 1, SS 1), (RU 2, SS 1), (RU 3, SS 1), and(RU 30, SS 6), respectively.

STA1 and STA200 may process the trigger frame 1302 received from the APand may transmit a random access PPDU 1304 and 1306, respectively, intheir allocated code-frequency resource. In an aspect, STA1 and STA200may transmit the random access PPDU 1304 and 1306, respectively, as anindication that they have data to send in the uplink. In contrast, inthis aspect, although STA2 and STA3 are allocated a code-frequencyresource, STA2 and STA3 do not send a random access PPDU since they donot have any data to send in the uplink. The AP may transmit a triggerframe 1308 that includes an indication of a random access type 6, whichincludes a mapping of resources allocated to STA2007. For instance,STA2007 may be allocated (RU 28, SS 4). In response to the trigger frame1308, STA2007 may transmit a random access PPDU 1310 (e.g., as anindication that STA2007 has data to send in the uplink).

In some cases, the random access PPDUs 1304, 1306, and 1310 may benon-data packets (e.g., 1304, 1306, 1310 have no data field). In thesecases, an NDP is used for STA1 and STA200's random access in response tothe trigger frame 1302, and an NDP is used for STA2007's random accessin response to the trigger frame 1308.

In an aspect, the same code-frequency resource may be allocated tostations associated with different random access types. As an exampledifferent from that shown in FIG. 13, the code-frequency resource (e.g.,RU 1, SSI) that is allocated to one station (e.g., STA1) associated withthe random access type 1 may also be allocated to a station (e.g.,STA2007) of another random access type.

It is noted that the ellipses between the STA3 and STA200 may indicatethat one or more additional stations or no stations are present betweenthe STA3 and STA200. Similarly, it is noted that the ellipses betweenthe STA200 and STA2007 may indicate that one or more additional stationsor no stations are present between the STA200 and STA2007. It is notedthat the ellipses between the random access PPDUs 1304 and 1306 and thetrigger frame 1308 may indicate that one or more additional frameexchanges or no frame exchanges are present between the random accessPPDUs 1304 and 1306 and the trigger frame 1308. For instance, the AP maytransmit trigger frames to stations associated with a random access typedifferent from random access type 1 and 6.

In some cases, the code-frequency resources of the random access PPDUcan be allocated to different access categories (ACs). For example, ifSTA1 has data in its AC voice (AC-VO) queue and STA2 has data in its ACbest effort (AC-BE) queue, STA1 may send a random access signal (e.g.,random access PPDU) using a set of code-frequency resources allocated toAC-VO and STA2 may send a random access signal using a set ofcode-frequency resources allocated to AC-BE. In an aspect, the allocatedcode-frequency resources may not need to be singular. In such a case,the station may select (e.g., pseudorandomly select) one of thecode-frequency resources for random access transmission.

In some cases, the random access resources assigned to one or morestations may be dependent on a lowest backoff timer value of an uplinktraffic enhanced distributed channel access function (EDCAF). Forexample, stations with the lowest backoff timer of 1 may use a set ofrandom access resources to transmit (e.g., potentially transmit) arandom access signal and stations with a lowest backoff timer of 4 mayuse a different set of random access resources to transmit (e.g.,potentially transmit) a random access signal. In such a case, the randomaccess resources assigned to a lower backoff timer value may beprioritized and assigned more resources compared to random accessresources available for higher backoff timer values. In an aspect, therandom access signal may contain information on the backoff timer ofeach non-empty AC queue.

In some aspects, a non-data carrying random access signal (e.g., thenon-data carrying random access signal described above) may allowmultiplexing a large number of resources in a single random access PPDUopportunity. In one aspect, a drawback, however, can be lack ofinformation conveyed to the AP. To overcome this drawback, a randomaccess procedure can be performed in a two-step approach, as describedbelow.

In a first step, the AP may transmit a trigger frame to solicit a randomaccess PPDU (e.g., short random access PPUD) from one or more stations.In a second step, the AP may transmit a trigger frame to solicit UL MUPPDUs containing data (e.g., HE-DATA) from the station(s) thattransmitted a random access PPDU(s) in the first step. In an aspect, theresources allocated in the first step may be smaller than the resourcesallocated in the second step. For instance, smaller and/or fewerfrequency subbands may be allocated to each station during the firststep.

FIG. 14 illustrates a schematic diagram of an example of exchanges offrames among wireless communication devices for UL MU transmission,where the two-step approach is utilized. The AP may transmit a triggerframe 1402. In an aspect, the trigger frame 1402 may be referred to as arandom access trigger frame or a random access trigger. In an aspect,the trigger frame 1402 may be utilized for soliciting random accesssignals (e.g., non-data carrying random access signals). The randomaccess signals may be non-data carrying random access signals (e.g., noHE-DATA field). In an aspect, the AP may allocate the resources utilizedby each station for random access signal transmission and indicate theallocated resources in the trigger frame 1402. For instance, the AP mayallocate resources to STA1, STA2, and STA3.

In some cases, the resources (e.g., frequency resource unites), code(s))that each station can use for random access signal transmission may beunique (e.g., orthogonal), such that each station is exclusivelyallocated its own respective resources. In some cases, the resourcesthat each station may use are shared between stations. In such cases,the total resources (e.g., potential resources to be allocated) aresufficiently large so as to be statistically sufficient to achieve a lowprobability of collision (e.g., to facilitate no two stations using thesame resources with high probability).

STA1 and STA3 may transmit random access PPDU 1404 and 1406,respectively. STA1 may transmit the random access PPDU 1404 using arandom access resource RA9 allocated to STA1 (e.g., in the trigger frame1402) for random access transmission. STA3 may transmit the randomaccess PPDU 1406 using a random access resource RA4. Each of RA9 and RA4may be associated with one or more resource unit indices and one or morespatial stream indices. In an aspect, RA9 and RA4 are used fortransmitting a STA specific portion of the random access PPDU 1404 and1406, respectively. In an aspect, STA1 and STA3 may transmit the randomaccess PPDU 1404 and 1406, respectively, to indicate that they have datato send in the uplink. In contrast, in this aspect, STA2 does not send arandom access PPDU since STA2 does not have any data to send in theuplink.

Once the AP receives the random access PPDUs 1404 and 1406, the AP maytransmit a second trigger frame 1408 to solicit uplink data from STA1and STA3. The trigger frame 1408 may include resource allocationinformation (e.g., resource unit, spatial code) to be utilized for datatransmission by STA1 and STA3. In response to the trigger frame 1408,STA1 and STA3 may transmit a PPDU 1410 and 1412 that contains data. ThePPDUs 1410 and 1412 may be transmitted based on respective resourcesallocated to STA1 and STA3. The AP may transmit an acknowledgement frame1414 (e.g., multi-user (MU) acknowledgement frame) upon receipt of thePPDUs 1410 and 1412.

In some aspects, the resources allocated for data transmission may belarger (e.g., larger resource unit(s)) than the resources allocated forrandom access transmission. In some cases, the AP may allocate resources(e.g., indicated using the trigger frame 1402) for a larger number ofstations for the random access transmission. The AP may then allocateresources (e.g., indicated using the second trigger frame 1408) to asmaller number of stations for the data transmission. For instance, theAP may allocate resources for data transmission for those stations thatindicated they have data to send (e.g., by sending PPDU 1404, 1406).

FIG. 15 illustrates a schematic diagram of another example of exchangesof frames among wireless communication devices for UL MU transmission,where the two-step approach is utilized.

The AP may transmit a trigger frame 1502 to station(s) associated with arandom access type A. The trigger frame 1502 may allocate resources tothe station(s) associated with the random access type A. In FIG. 15, thestation(s) associated with the random access type A may include STA1 andSTA3. In response to the trigger frame 1502, STA1 and STA3 may transmita random access PPDU 1504 and 1506, respectively. STA1 may transmit therandom access PPDU 1504 using a random access resource RA9 allocated toSTA1 (e.g., in the trigger frame 1502) for random access transmission.STA3 may transmit the random access PPDU 1506 using a random accessresource RA4. The random access PPDU 1504 may include a common preambleportion 1504A and a STA-specific portion 1504B. The random access PPDU1506 may include a common preamble portion 1506A and a STA-specificportion 1506B. The common preamble portions 1504A and 1506A may occupythe entire channel bandwidth of the random access PPDUs 1504 and 1506,respectively. The STA-specific portions 1504B and 1506B may betransmitted using RA9 and RA4, respectively.

The AP may transmit a trigger frame 1508 to station(s) associated with arandom access type B. The trigger frame 1508 may allocate resources tothe station(s) associated with the random access type B. In FIG. 15, thestation(s) associated with the random access type B may include STA2. Inresponse to the trigger frame 1508, STA2 may transmit a random accessPPDU 1510 that includes a common preamble portion 1510A and aSTA-specific portion 1510B. The STA-specific portion 1510B may betransmitted using a random access resource RA3. In an aspect, the randomaccess PPDUs 1504, 1506, and 1510 may be non-data carrying random accessPPDUs (e.g., no data field, no HE-DATA field).

The AP may transmit a trigger frame 1512 to solicit uplink data fromSTA1, STA2, and STA3. The trigger frame 1512 may include resourceallocation information (e.g., resource unit, spatial code) to beutilized for data transmission by STA1, STA2, and STA3. In response tothe trigger frame 1512, STA1, STA2, and STA3 may transmit a PPDU 1514,1516, and 1518, respectively, that contains data. The PPDUs 1514, 1516,and 1518 may be transmitted based on respective resources allocated toSTA1, STA2, and STA3 by the trigger frame 1512. The AP may transmit anacknowledgement frame 1520 (e.g., multi-user (MU) acknowledgement frame)upon receipt of the PPDUs 1514, 1516, and 1518.

Although FIG. 15 illustrates an example in which the AP transmitstrigger frames (e.g., 1502, 1508) to solicit random access PPDUs (e.g.,1504, 1506, 1510) from stations associated with two different randomaccess types (e.g., type A, type B), the AP may transmit trigger framesto solicit random access PPDUs from more, fewer, and/or different randomaccess types than those shown in FIG. 15. In an aspect, the AP maytransmit trigger frames (e.g., 1512) to solicit uplink data fromstations of different random access types (e.g., STA1 and STA3 of randomaccess type A, STA2 of random access type B).

The horizontal dimension in FIGS. 10, 11, 13, 14, and 15 represent thetime dimension. In some aspects, a time interval between any two framesin FIGS. 13 through 15 may be an SIFS, PIFS, or any other time interval.

Referring to FIGS. 6, 7, 13, 14, and 15, in one or more implementations,a trigger frame (e.g., 1302, 1308, 1402, 1408, 1502, 1508, 1512) mayinclude all or some of the fields of an HE frame 600, and an uplinkrandom access frame (e.g., 1304, 1306, 1310, 1404, 1406, 1504, 1506,1510) may include all or some of the fields of a random access PPDU 700,excluding the HE-DATA field. In one or more implementations, an uplinkdata frame (e.g., 1410, 1412, 1514, 1516, 1518) may include the HE-DATAfield of a random access PPDU 700 and some or all of the other fields ofthe random access PPDU 700.

It should be noted that like reference numerals may designate likeelements. These components with the same reference numerals have certaincharacteristics that are the same, but as different figures illustratedifferent examples, the same reference numeral does not indicate that acomponent with the same reference numeral has the exact samecharacteristics. While the same reference numerals are used for certaincomponents, examples of differences with respect to a component aredescribed throughout this disclosure.

The embodiments provided herein have been described with reference to awireless LAN system; however, it should be understood that thesesolutions are also applicable to other network environments, such ascellular telecommunication networks, wired networks, etc.

An embodiment of the present disclosure may be an article of manufacturein which a non-transitory machine-readable medium (such asmicroelectronic memory) has stored thereon instructions which programone or more data processing components (generically referred to here asa “processor” or “processing unit”) to perform the operations describedherein. In other embodiments, some of these operations may be performedby specific hardware components that contain hardwired logic (e.g.,dedicated digital filter blocks and state machines). Those operationsmay alternatively be performed by any combination of programmed dataprocessing components and fixed hardwired circuit components.

In some cases, an embodiment of the present disclosure may be anapparatus (e.g., an AP STA, a non-AP STA, or another network orcomputing device) that includes one or more hardware and software logicstructure for performing one or more of the operations described herein.For example, as described above, the apparatus may include a memoryunit, which stores instructions that may be executed by a hardwareprocessor installed in the apparatus. The apparatus may also include oneor more other hardware or software elements, including a networkinterface, a display device, etc.

FIGS. 16A and 16B illustrate flow charts of examples of methods forfacilitating wireless communication. For explanatory and illustrationpurposes, the example processes 1610 and 1620 may be performed by thewireless communication devices 111-115 of FIG. 1 and their componentssuch as a baseband processor 210, a MAC processor 211, a MAC softwareprocessing unit 212, a MAC hardware processing unit 213, a PHY processor215, a transmitting signal processing unit 280 and/or a receiving signalprocessing unit 290; however, the example processes 1610 and 1620 arenot limited to the wireless communication devices 111-115 of FIG. 1 ortheir components, and the example processes 1610 and 1620 may beperformed by some of the devices shown in FIG. 1, or other devices orcomponents. Further for explanatory and illustration purposes, theblocks of the example processes 1610 and 1620 are described herein asoccurring in serial or linearly. However, multiple blocks of the exampleprocesses 1610 and 1620 may occur in parallel. In addition, the blocksof the example processes 1610 and 1620 need not be performed in theorder shown and/or one or more of the blocks/actions of the exampleprocesses 1610 and 1620 need not be performed.

Various examples of aspects of the disclosure are described below asclauses for convenience. These are provided as examples, and do notlimit the subject technology. As an example, some of the clausesdescribed below are illustrated in FIGS. 16A and 16B.

Clause A. A station for facilitating communication in a wireless networkfor multi-user transmission, the station comprising: one or morememories; and one or more processors coupled to the one or morememories, the one or more processors configured to cause: processing afirst trigger frame received from an access point, wherein the firsttrigger frame schedules a first uplink multi-user transmission andindicates a plurality of resources for indicating existence of data tobe sent to the access point; and transmitting, during the first uplinkmulti-user transmission to the access point and in response to the firsttrigger frame, a first uplink frame that has no data field and that hasa signal indicating existence of data to be sent from the station to theaccess point, wherein the transmitting comprises transmitting the signalon a first resource of the plurality of resources.

Clause B. An access point for facilitating communication in a wirelessnetwork for multi-user transmission, the access point comprising: one ormore memories; and one or more processors coupled to the one or morememories, the one or more processors configured to cause: transmitting afirst trigger frame to one or more stations, to schedule an uplinkmulti-user transmission with the one or more stations, wherein the firsttrigger frame indicates a plurality of resources for indicatingexistence of data to be sent to the access point; and receiving, duringthe uplink multi-user transmission, a first uplink frame from a firststation of the one or more stations, wherein the first uplink frame hasno data field and has a signal indicating existence of data to be sentfrom the first station to the access point, and wherein the receivingcomprises receiving the signal on a first resource of the plurality ofresources.

Clause C. A computer-implemented method of facilitating communication ina wireless network for multi-user transmission, the method comprising:processing a first trigger frame received from an access point, whereinthe first trigger frame is for scheduling a first uplink multi-usertransmission and indicates a plurality of resources for indicatingexistence of data to be sent to the access point; and transmitting,during the first uplink multiuser transmission to the access point andin response to the first trigger frame, a first uplink frame that has nodata field and that has a signal indicating existence of data to be sentfrom a station to the access point, wherein the signal is sent on afirst resource of the plurality of resources.

In one or more aspects, additional clauses are described below.

A method comprising one or more methods or operations described herein.

An apparatus or a station comprising one or more memories (e.g., 240,one or more internal, external or remote memories, or one or moreregisters) and one or more processors (e.g., 210) coupled to the one ormore memories, the one or more processors configured to cause theapparatus to perform one or more methods or operations described herein.

An apparatus or a station comprising one or more memories (e.g., 240,one or more internal, external or remote memories, or one or moreregisters) and one or more processors (e.g., 210 or one or moreportions), wherein the one or more memories store instructions that,when executed by the one or more processors, cause the one or moreprocessors to perform one or more methods or operations describedherein.

An apparatus or a station comprising means (e.g., 210) adapted forperforming one or more methods or operations described herein.

A computer-readable storage medium (e.g., 240, one or more internal,external or remote memories, or one or more registers) comprisinginstructions stored therein, the instructions comprising code forperforming one or more methods or operations described herein.

A computer-readable storage medium (e.g., 240, one or more internal,external or remote memories, or one or more registers) storinginstructions that, when executed by one or more processors (e.g., 210 orone or more portions), cause the one or more processors to perform oneor more methods or operations described herein.

In one aspect, a method may be an operation, an instruction, or afunction and vice versa. In one aspect, a clause may be amended toinclude some or all of the words (e.g., instructions, operations,functions, or components) recited in other one or more clauses, one ormore sentences, one or more phrases, one or more paragraphs, and/or oneor more claims.

To illustrate the interchangeability of hardware and software, itemssuch as the various illustrative blocks, modules, components, methods,operations, instructions, and algorithms have been described generallyin terms of their functionality. Whether such functionality isimplemented as hardware or software depends upon the particularapplication and design constraints imposed on the overall system.Skilled artisans may implement the described functionality in varyingways for each particular application.

A reference to an element in the singular is not intended to mean oneand only one unless specifically so stated, but rather one or more. Forexample, “a” module may refer to one or more modules. An elementproceeded by “a,” “an,” “the,” or “said” does not, without furtherconstraints, preclude the existence of additional same elements.

Headings and subheadings, if any, are used for convenience only and donot limit the invention. The word exemplary is used to mean serving asan example or illustration. To the extent that the term include, have,or the like is used, such term is intended to be inclusive in a mannersimilar to the term comprise as comprise is interpreted when employed asa transitional word in a claim. Relational terms such as first andsecond and the like may be used to distinguish one entity or action fromanother without necessarily requiring or implying any actual suchrelationship or order between such entities or actions.

Phrases such as an aspect, the aspect, another aspect, some aspects, oneor more aspects, an implementation, the implementation, anotherimplementation, some implementations, one or more implementations, anembodiment, the embodiment, another embodiment, some embodiments, one ormore embodiments, a configuration, the configuration, anotherconfiguration, some configurations, one or more configurations, thesubject technology, the disclosure, the present disclosure, othervariations thereof and alike are for convenience and do not imply that adisclosure relating to such phrase(s) is essential to the subjecttechnology or that such disclosure applies to all configurations of thesubject technology. A disclosure relating to such phrase(s) may apply toall configurations, or one or more configurations. A disclosure relatingto such phrase(s) may provide one or more examples. A phrase such as anaspect or some aspects may refer to one or more aspects and vice versa,and this applies similarly to other foregoing phrases.

A phrase “at least one of” preceding a series of items, with the terms“and” or “or” to separate any of the items, modifies the list as awhole, rather than each member of the list. The phrase “at least one of”does not require selection of at least one item; rather, the phraseallows a meaning that includes at least one of anyone of the items,and/or at least one of any combination of the items, and/or at least oneof each of the items. By way of example, each of the phrases “at leastone of A, B, and C” or “at least one of A, B, or C” refers to only A,only B, or only C; any combination of A, B, and C; and/or at least oneof each of A, B, and C.

It is understood that the specific order or hierarchy of steps,operations, or processes disclosed is an illustration of exemplaryapproaches. Unless explicitly stated otherwise, it is understood thatthe specific order or hierarchy of steps, operations, or processes maybe performed in different order. Some of the steps, operations, orprocesses may be performed simultaneously. The accompanying methodclaims, if any, present elements of the various steps, operations orprocesses in a sample order, and are not meant to be limited to thespecific order or hierarchy presented. These may be performed in serial,linearly, in parallel or in different order. It should be understoodthat the described instructions, operations, and systems can generallybe integrated together in a single software/hardware product or packagedinto multiple software/hardware products.

The disclosure is provided to enable any person skilled in the art topractice the various aspects described herein. In some instances,well-known structures and components are shown in block diagram form inorder to avoid obscuring the concepts of the subject technology. Thedisclosure provides various examples of the subject technology, and thesubject technology is not limited to these examples. Variousmodifications to these aspects will be readily apparent to those skilledin the art, and the principles described herein may be applied to otheraspects.

All structural and functional equivalents to the elements of the variousaspects described throughout the disclosure that are known or later cometo be known to those of ordinary skill in the art are expresslyincorporated herein by reference and are intended to be encompassed bythe claims. Moreover, nothing disclosed herein is intended to bededicated to the public regardless of whether such disclosure isexplicitly recited in the claims. No claim element is to be construedunder the provisions of 35 U.S.C. § 112, sixth paragraph, unless theelement is expressly recited using a phrase means for or, in the case ofa method claim, the element is recited using the phrase step for.

The title, background, brief description of the drawings, abstract, anddrawings are hereby incorporated into the disclosure and are provided asillustrative examples of the disclosure, not as restrictivedescriptions. It is submitted with the understanding that they will notbe used to limit the scope or meaning of the claims. In addition, in thedetailed description, it can be seen that the description providesillustrative examples and the various features are grouped together invarious implementations for the purpose of streamlining the disclosure.The method of disclosure is not to be interpreted as reflecting anintention that the claimed subject matter requires more features thanare expressly recited in each claim. Rather, as the following claimsreflect, inventive subject matter lies in less than all features of asingle disclosed configuration or operation. The following claims arehereby incorporated into the detailed description, with each claimstanding on its own as a separately claimed subject matter.

The claims are not intended to be limited to the aspects describedherein, but are to be accorded the full scope consistent with thelanguage claims and to encompass all legal equivalents. Notwithstanding,none of the claims are intended to embrace subject matter that fails tosatisfy the requirements of the applicable patent law, nor should theybe interpreted in such a way.

We claim:
 1. A station for facilitating communication in a wirelessnetwork for multi-user transmission, the station comprising: one or morememories; and one or more processors coupled to the one or morememories, the one or more processors configured to: process a firstrequest for buffer status received from an access point, wherein thefirst request for buffer status schedules a first uplink multi-usertransmission and indicates a plurality of resources that indicatesexistence of data to be sent to the access point; and transmit, duringthe first uplink multi-user transmission to the access point and inresponse to the first request for buffer status, a first uplink nulldata packet and that comprises a signal that indicates existence of datato be sent from the station to the access point, wherein the one or moreprocessors transmits the first uplink null data packet comprises the oneor more processors configured to transmit the signal on a first resourceof the plurality of resources.
 2. The station of claim 1, wherein eachof the plurality of resources is associated with a frequency resourceunit of a plurality of frequency resource units and a code of aplurality of codes, wherein the first resource is associated with afirst frequency resource unit of the plurality of frequency resourceunits and a first code of the plurality of codes.
 3. The station ofclaim 2, wherein each code of the plurality of codes is orthogonal toeach of the other codes of the plurality of codes.
 4. The station ofclaim 2, wherein each code of the plurality of codes represent a spatialstream in a plurality of spatial streams.
 5. The station of claim 1,wherein the first request for buffer status comprises a trigger frame.6. An access point (AP) for facilitating communication in a wirelessnetwork for multi-user transmission, the AP comprising: one or morememories; and one or more processors, coupled to the one or morememories, the one or more processors configured to: send a first requestfor buffer status to a non-AP station, wherein the first request forbuffer status schedules a first uplink multi-user transmission andindicates a plurality of resources that indicates existence of data tobe sent to the AP; and receive, during the first uplink multi-usertransmission from the non-AP station and in response to the firstrequest for buffer status, a first uplink null data packet and that hasa signal that indicates existence of data to be sent from the station tothe AP, wherein the one or more processors receive the first uplink nulldata packet comprises the one or more processors configured to receivethe signal on a first resource of the plurality of resources.
 7. Theaccess point of claim 6, wherein: each of the plurality of resources isassociated with a frequency resource unit of a plurality of frequencyresource units and a code of a plurality of codes, wherein the firstresource is associated with a first frequency resource unit of theplurality of frequency resource units and a first code of the pluralityof codes.
 8. The access point of claim 7, wherein each code of theplurality of codes is orthogonal to each of the other codes of theplurality of codes.
 9. The access point of claim 7, wherein each code ofthe plurality of codes represents a spatial stream in a plurality ofspatial streams.
 10. The access point of claim 6, wherein the firstrequest for buffer status comprises a trigger frame.